1. Field of the Invention
The invention relates to smoke detectors. More particularly, the invention relates to methods and circuits for converting battery powered smoke detectors to AC power with battery back-up and to kits incorporating the methods and circuits.
2. State of the Art
Today, smoke detectors are commonly found in most homes. Local building codes and insurance companies often require that smoke detectors be installed in newly constructed buildings and in commercial buildings. Moreover, public awareness of the benefits of smoke detectors and their relatively low cost have made them universally popular. Almost all household smoke detectors are battery powered in order to simplify installation by the homeowner. Prior art FIG. 1 shows a typical battery powered smoke detector 10 found in most homes. The smoke detector 10 includes a circular base 12 having mounting holes 14 and 16. A circuit board 18 is attached to the base 12 and includes a smoke sensor 20 and a sound transducer 22. A 9-volt battery 24 is electrically coupled to the circuit board by battery clips 26. The smoke detector 10 is easy to install, is relatively unobtrusive, and is very reliable provided that the battery is in good condition. Indeed, many homeowners now realize that while the battery powered smoke detector is easy to install, it is difficult to maintain. The battery should be checked once a month and usually needs to be replaced once or twice a year. Testing and replacing the battery often requires the use of a ladder since smoke detectors are advantageously installed on ceilings or high on walls in order to detect smoke which rises to the ceiling. Since most homes now contain at least one smoke detector on each level of the house, a monthly ritual of carrying a ladder to each smoke detector and climbing up and down the ladder several times is bothersome and can also be hazardous. As a result, most homeowners simply do not bother to test the batteries in the smoke detectors. This, of course, creates an even greater hazard that the smoke detector will fail due to a dead or weak battery.
Commercial smoke detectors, on the other hand, are almost always AC powered with a battery back-up. While these smoke detectors are more complicated to install, they are virtually mandatory in a commercial building where dozens or hundreds of smoke detectors are used and where it would be extremely time consuming to test so many batteries on a monthly basis.
Recently, AC powered smoke detectors have become available for home use and some homeowners have replaced their battery powered smoke detectors with AC powered detectors. Unfortunately, the battery powered smoke detectors must be discarded since there is presently no way to adapt them for use with AC power.